Tomcat example source code file (StandardHostValve.java)

This example Tomcat source code file (StandardHostValve.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Tomcat tags/keywords

context, context, errorpage, exception, http, integer, io, ioexception, processing, request, response, response, servlet, servletexception, string, string, throwable, throwable

The Tomcat StandardHostValve.java source code

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */


package org.apache.catalina.core;


import java.io.IOException;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletResponse;

import org.apache.catalina.CometEvent;
import org.apache.catalina.Context;
import org.apache.catalina.Globals;
import org.apache.catalina.Wrapper;
import org.apache.catalina.connector.ClientAbortException;
import org.apache.catalina.connector.Request;
import org.apache.catalina.connector.Response;
import org.apache.catalina.deploy.ErrorPage;
import org.apache.catalina.util.RequestUtil;
import org.apache.catalina.util.StringManager;
import org.apache.catalina.valves.ValveBase;
import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;


/**
 * Valve that implements the default basic behavior for the
 * <code>StandardHost container implementation.
 * <p>
 * <b>USAGE CONSTRAINT:  This implementation is likely to be useful only
 * when processing HTTP requests.
 *
 * @author Craig R. McClanahan
 * @author Remy Maucherat
 * @version $Revision: 487694 $ $Date: 2006-12-15 23:30:51 +0100 (ven., 15 déc. 2006) $
 */

final class StandardHostValve
    extends ValveBase {


    private static Log log = LogFactory.getLog(StandardHostValve.class);

    // ----------------------------------------------------- Instance Variables


    /**
     * The descriptive information related to this implementation.
     */
    private static final String info =
        "org.apache.catalina.core.StandardHostValve/1.0";


    /**
     * The string manager for this package.
     */
    private static final StringManager sm =
        StringManager.getManager(Constants.Package);


    // ------------------------------------------------------------- Properties


    /**
     * Return descriptive information about this Valve implementation.
     */
    public String getInfo() {

        return (info);

    }


    // --------------------------------------------------------- Public Methods


    /**
     * Select the appropriate child Context to process this request,
     * based on the specified request URI.  If no matching Context can
     * be found, return an appropriate HTTP error.
     *
     * @param request Request to be processed
     * @param response Response to be produced
     * @param valveContext Valve context used to forward to the next Valve
     *
     * @exception IOException if an input/output error occurred
     * @exception ServletException if a servlet error occurred
     */
    public final void invoke(Request request, Response response)
        throws IOException, ServletException {

        // Select the Context to be used for this Request
        Context context = request.getContext();
        if (context == null) {
            response.sendError
                (HttpServletResponse.SC_INTERNAL_SERVER_ERROR,
                 sm.getString("standardHost.noContext"));
            return;
        }

        // Bind the context CL to the current thread
        if( context.getLoader() != null ) {
            // Not started - it should check for availability first
            // This should eventually move to Engine, it's generic.
            Thread.currentThread().setContextClassLoader
                    (context.getLoader().getClassLoader());
        }

        // Ask this Context to process this request
        context.getPipeline().getFirst().invoke(request, response);

        // Access a session (if present) to update last accessed time, based on a
        // strict interpretation of the specification
        if (Globals.STRICT_SERVLET_COMPLIANCE) {
            request.getSession(false);
        }

        // Error page processing
        response.setSuspended(false);

        Throwable t = (Throwable) request.getAttribute(Globals.EXCEPTION_ATTR);

        if (t != null) {
            throwable(request, response, t);
        } else {
            status(request, response);
        }

        // Restore the context classloader
        Thread.currentThread().setContextClassLoader
            (StandardHostValve.class.getClassLoader());

    }


    /**
     * Process Comet event.
     *
     * @param request Request to be processed
     * @param response Response to be produced
     * @param valveContext Valve context used to forward to the next Valve
     *
     * @exception IOException if an input/output error occurred
     * @exception ServletException if a servlet error occurred
     */
    public final void event(Request request, Response response, CometEvent event)
        throws IOException, ServletException {

        // Select the Context to be used for this Request
        Context context = request.getContext();

        // Bind the context CL to the current thread
        if( context.getLoader() != null ) {
            // Not started - it should check for availability first
            // This should eventually move to Engine, it's generic.
            Thread.currentThread().setContextClassLoader
                    (context.getLoader().getClassLoader());
        }

        // Ask this Context to process this request
        context.getPipeline().getFirst().event(request, response, event);

        // Access a session (if present) to update last accessed time, based on a
        // strict interpretation of the specification
        if (Globals.STRICT_SERVLET_COMPLIANCE) {
            request.getSession(false);
        }

        // Error page processing
        response.setSuspended(false);

        Throwable t = (Throwable) request.getAttribute(Globals.EXCEPTION_ATTR);

        if (t != null) {
            throwable(request, response, t);
        } else {
            status(request, response);
        }

        // Restore the context classloader
        Thread.currentThread().setContextClassLoader
            (StandardHostValve.class.getClassLoader());

    }


    // ------------------------------------------------------ Protected Methods


    /**
     * Handle the specified Throwable encountered while processing
     * the specified Request to produce the specified Response.  Any
     * exceptions that occur during generation of the exception report are
     * logged and swallowed.
     *
     * @param request The request being processed
     * @param response The response being generated
     * @param throwable The exception that occurred (which possibly wraps
     *  a root cause exception
     */
    protected void throwable(Request request, Response response,
                             Throwable throwable) {
        Context context = request.getContext();
        if (context == null)
            return;

        Throwable realError = throwable;

        if (realError instanceof ServletException) {
            realError = ((ServletException) realError).getRootCause();
            if (realError == null) {
                realError = throwable;
            }
        }

        // If this is an aborted request from a client just log it and return
        if (realError instanceof ClientAbortException ) {
            if (log.isDebugEnabled()) {
                log.debug
                    (sm.getString("standardHost.clientAbort",
                        realError.getCause().getMessage()));
            }
            return;
        }

        ErrorPage errorPage = findErrorPage(context, throwable);
        if ((errorPage == null) && (realError != throwable)) {
            errorPage = findErrorPage(context, realError);
        }

        if (errorPage != null) {
            response.setAppCommitted(false);
            request.setAttribute
                (ApplicationFilterFactory.DISPATCHER_REQUEST_PATH_ATTR,
                 errorPage.getLocation());
            request.setAttribute(ApplicationFilterFactory.DISPATCHER_TYPE_ATTR,
                              new Integer(ApplicationFilterFactory.ERROR));
            request.setAttribute
                (Globals.STATUS_CODE_ATTR,
                 new Integer(HttpServletResponse.SC_INTERNAL_SERVER_ERROR));
            request.setAttribute(Globals.ERROR_MESSAGE_ATTR,
                              throwable.getMessage());
            request.setAttribute(Globals.EXCEPTION_ATTR,
                              realError);
            Wrapper wrapper = request.getWrapper();
            if (wrapper != null)
                request.setAttribute(Globals.SERVLET_NAME_ATTR,
                                  wrapper.getName());
            request.setAttribute(Globals.EXCEPTION_PAGE_ATTR,
                                 request.getRequestURI());
            request.setAttribute(Globals.EXCEPTION_TYPE_ATTR,
                              realError.getClass());
            if (custom(request, response, errorPage)) {
                try {
                    response.flushBuffer();
                } catch (IOException e) {
                    container.getLogger().warn("Exception Processing " + errorPage, e);
                }
            }
        } else {
            // A custom error-page has not been defined for the exception
            // that was thrown during request processing. Check if an
            // error-page for error code 500 was specified and if so,
            // send that page back as the response.
            response.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
            // The response is an error
            response.setError();

            status(request, response);
        }


    }


    /**
     * Handle the HTTP status code (and corresponding message) generated
     * while processing the specified Request to produce the specified
     * Response.  Any exceptions that occur during generation of the error
     * report are logged and swallowed.
     *
     * @param request The request being processed
     * @param response The response being generated
     */
    protected void status(Request request, Response response) {

        int statusCode = response.getStatus();

        // Handle a custom error page for this status code
        Context context = request.getContext();
        if (context == null)
            return;

        /* Only look for error pages when isError() is set.
         * isError() is set when response.sendError() is invoked. This
         * allows custom error pages without relying on default from
         * web.xml.
         */
        if (!response.isError())
            return;

        ErrorPage errorPage = context.findErrorPage(statusCode);
        if (errorPage != null) {
            response.setAppCommitted(false);
            request.setAttribute(Globals.STATUS_CODE_ATTR,
                              new Integer(statusCode));

            String message = RequestUtil.filter(response.getMessage());
            if (message == null)
                message = "";
            request.setAttribute(Globals.ERROR_MESSAGE_ATTR, message);
            request.setAttribute
                (ApplicationFilterFactory.DISPATCHER_REQUEST_PATH_ATTR,
                 errorPage.getLocation());
            request.setAttribute(ApplicationFilterFactory.DISPATCHER_TYPE_ATTR,
                              new Integer(ApplicationFilterFactory.ERROR));


            Wrapper wrapper = request.getWrapper();
            if (wrapper != null)
                request.setAttribute(Globals.SERVLET_NAME_ATTR,
                                  wrapper.getName());
            request.setAttribute(Globals.EXCEPTION_PAGE_ATTR,
                                 request.getRequestURI());
            if (custom(request, response, errorPage)) {
                try {
                    response.flushBuffer();
                } catch (ClientAbortException e) {
                    // Ignore
                } catch (IOException e) {
                    container.getLogger().warn("Exception Processing " + errorPage, e);
                }
            }
        }

    }


    /**
     * Find and return the ErrorPage instance for the specified exception's
     * class, or an ErrorPage instance for the closest superclass for which
     * there is such a definition.  If no associated ErrorPage instance is
     * found, return <code>null.
     *
     * @param context The Context in which to search
     * @param exception The exception for which to find an ErrorPage
     */
    protected static ErrorPage findErrorPage
        (Context context, Throwable exception) {

        if (exception == null)
            return (null);
        Class clazz = exception.getClass();
        String name = clazz.getName();
        while (!Object.class.equals(clazz)) {
            ErrorPage errorPage = context.findErrorPage(name);
            if (errorPage != null)
                return (errorPage);
            clazz = clazz.getSuperclass();
            if (clazz == null)
                break;
            name = clazz.getName();
        }
        return (null);

    }


    /**
     * Handle an HTTP status code or Java exception by forwarding control
     * to the location included in the specified errorPage object.  It is
     * assumed that the caller has already recorded any request attributes
     * that are to be forwarded to this page.  Return <code>true if
     * we successfully utilized the specified error page location, or
     * <code>false if the default error report should be rendered.
     *
     * @param request The request being processed
     * @param response The response being generated
     * @param errorPage The errorPage directive we are obeying
     */
    protected boolean custom(Request request, Response response,
                             ErrorPage errorPage) {

        if (container.getLogger().isDebugEnabled())
            container.getLogger().debug("Processing " + errorPage);

        request.setPathInfo(errorPage.getLocation());

        try {

            // Reset the response if possible (else IllegalStateException)
            //hres.reset();
            // Reset the response (keeping the real error code and message)
            Integer statusCodeObj =
                (Integer) request.getAttribute(Globals.STATUS_CODE_ATTR);
            int statusCode = statusCodeObj.intValue();
            String message =
                (String) request.getAttribute(Globals.ERROR_MESSAGE_ATTR);
            response.reset(statusCode, message);

            // Forward control to the specified location
            ServletContext servletContext =
                request.getContext().getServletContext();
            RequestDispatcher rd =
                servletContext.getRequestDispatcher(errorPage.getLocation());
            rd.forward(request.getRequest(), response.getResponse());

            // If we forward, the response is suspended again
            response.setSuspended(false);

            // Indicate that we have successfully processed this custom page
            return (true);

        } catch (Throwable t) {

            // Report our failure to process this custom page
            container.getLogger().error("Exception Processing " + errorPage, t);
            return (false);

        }

    }


}